An efficient NBTI-aware wake-up strategy for power-gated designs

The wake-up process of a power-gated design may induce an excessive surge current and threaten the signal integrity. A proper wake-up sequence should be carefully designed to avoid surge current violations. On the other hand, PMOS sleep transistors may suffer from the negative-bias temperature instability (NBTI) effect which results in decreased driving current. Conventional wake-up sequence decision approaches do not consider the NBTI effect, which may result in a longer or unacceptable wake-up time after circuit aging. Therefore, in this paper, we propose a novel NBTI-aware wake-up strategy to reduce the average wake-up time within a circuit lifetime. Our strategy first finds a set of proper wake-up sequences for different aging scenarios (i.e. after a certain period of aging), and then dynamically reconfigures the wake-up sequences at runtime. The experimental results show that compared to a traditional fixed wake-up sequence approach, our strategy can reduce average wake-up time by as much as 45.04% with only 3.7% extra area overhead for the reconfiguration structure.